Gamow-Teller transitions of neutron-rich $N=82,81$ nuclei by shell-model calculations

TL;DR

This study uses advanced shell-model calculations to accurately predict the beta-decay half-lives and Gamow-Teller strength distributions of neutron-rich N=82 and 81 nuclei, crucial for understanding r-process nucleosynthesis.

Contribution

It introduces a new shell-model Hamiltonian that successfully describes spectra and half-lives of neutron-rich isotones around N=82 and 81 in a unified framework.

Findings

Low-lying Gamow-Teller strength peaks significantly influence half-lives.

Peak strength is dominated by ν 0g_{7/2} to π 0g_{9/2} transitions.

Proton deficiency enhances the low-energy Gamow-Teller strength due to reduced Pauli blocking.

Abstract

$\beta$-decay half-lives of neutron-rich nuclei around $N=82$ are key data to understand the $r$-process nucleosynthesis. We performed large-scale shell-model calculations in this region using a newly constructed shell-model Hamiltonian, and successfully described the low-lying spectra and half-lives of neutron-rich $N=82$ and $N=81$ isotones with $Z=42-49$ in a unified way. We found that their Gamow-Teller strength distributions have a peak in the low-excitation energies, which significantly contributes to the half-lives. This peak, dominated by $\nu 0g_{7/2} \to \pi 0g_{9/2}$ transitions, is enhanced on the proton deficient side because the Pauli-blocking effect caused by occupying the valence proton $0g_{9/2}$ orbit is weakened.